Downhole tools treated by plasma electrolytic oxidation

ABSTRACT

A downhole tool comprising a body made of aluminum material, dissolvable material or light alloy material having a coating formed by the plasma electrolytic oxidation process. The tool is a slip, a drag block, a button or any tool with wear blocks to get drag or keep the tool centered.

RELATED PRIORITY DATE APPLICATION

This application claims the benefit under 35 U.S.C. 119(e) of the U.S. provisional application Ser. No. 62/934,207 filed on Nov. 12, 2019.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of oil tools for the completion of oil and gas wellbores and, more particularly, to the field of downhole tools that facilitate the setting and anchoring of downhole tools for wellbore isolation. Still more particularly, the present invention discloses tools such as slips, drag blocks, and buttons that include a hardened area formed by plasma electrolytic oxidation treatment.

BACKGROUND OF THE INVENTION

In the drilling or reworking of oil wells, a great variety of downhole tools are used. The use of plugs and packers in downhole oil and gas operations are well known. During completion or well intervention, a plug is used to isolate a part of the casing from another part. For instance, when a job is carried out on the upper section of the well, the lower part of the interior of the casing must be isolated and plugged, i.e. zonal isolation in a well. In another operation, it is often desirable to seal tubing or other pipe in the casing of the well, such as when it is desired to pump cement or other slurry down the tubing and force the slurry out into a formation. It thus becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well. In those operations, downhole tools referred to as packers and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas.

These downhole tools have drill able components made from metallic or non-metallic materials, such as soft steel, cast iron, engineering grade plastics, and composite materials and further having buttons incorporated into anti-slip elements which facilitate the setting and anchoring of downhole tools such as a drill able packer and a bridge plug tools in wellbores.

These tools oftentimes utilize slips that are used for anchoring. Slips are either wicker or flat edge slips. Depending on the tool and application, slips are presently manufactured from steel, cast iron, composite or dissolvable material. Slips manufactured from steel can either be a wicker design or a flat wedge with carbide inserts. The wicker and flat edge slips are manufactured from steel which is heat treated to a Rockwell of 55 C or greater. Drag blocks are also typically made of steel with carbide inserts for wear resistance.

In the case of cement retainers, the wickers are manufactured from cast iron compounds and are flame hardened so that they have the required strength to bite into the pipe or casing.

Historically, steel was used to manufacture slips because of the durability and strength requirements. In recent years, composites and dissolvable material were developed to replace the steel. The composite and dissolvable material are used to take advantage of them being easily removable from the well, they still require the use of carbide or ceramic inserts to obtain the holding forces required.

One disadvantage of the use of steel, cast iron, ceramic or carbide is that they are heavy and are hard to remove after completion of the service performed.

It is also well known that cylindrically shaped inserts, or buttons, may be placed in slip elements, especially when such slip elements are made of a non-metallic material such as plastic composite material, to enhance the ability of the slip elements to engage the well casing. The buttons must be of sufficient hardness to be able to partially penetrate, or bite into, the surface of the well casing which is typically steel. However, especially in the case of downhole tools being constructed of materials that lend themselves to being easily drilled from the wellbore once a given operation involving the tool has been performed, the buttons must not be so hard or so tough to resist drilling or fouling of the cutting surfaces of the drilling bit or milling bit.

Currently, it is known that buttons made of zirconia ceramic materials offer to a certain extent, the desirable characteristics of being of a sufficient hardness to bite in the casing upon setting the tool, but are not so tough as not to be drill able when it comes time to remove the tool from the wellbore. However, it has become evident that the first portion of the button to contact the casing which is usually the most protruding or leading edge of the cylindrically shaped buttons made of such zirconia ceramic materials are brittle and therefore prone, if not expected, to chip or fracture as the slip element engages with the well casing. Many times, such chipping along the leading edge does not degrade the anti-slipping ability of the tool to a level that the tool actually slips in the casing under normal conditions. However, under extremely high pressures or temperatures the undesired chipping could adversely affect the anti-slip performance of the slip elements because the button would not be able to bite as deeply into the casing as would be possible if the leading edge were not chipped during the setting of the tool.

In the past, to overcome some of the problems associated with zirconia ceramic buttons, tungsten-carbide material has been used to form buttons. The tungsten carbide buttons offer enhanced anti-chipping characteristics but do so at the expense of not being as easy to drill or mill as the zirconia buttons when destructively removing the tool from the cased wellbore due to the extreme hardness, higher density, and toughness of the tungsten carbide buttons. Such drilling and milling problems include the tungsten carbide buttons fouling, dulling, difficulty in circulating pieces of the buttons within fluids that may be present in the well bore, and the tungsten carbide buttons simply resisting the cutting edges of the drilling or milling tools. Such resistance causes increased costs associated with the rig and tool crews having to expend more time to manipulate the drill string in order to successfully drill, or mill, the tool from the wellbore.

Thus, there remains a need in the art to identify slip button materials that are sufficiently hard to resist chipping upon biting into the wellbore casing yet not be so tough as to unduly resist drilling or milling when it comes time for the tool having such buttons to be destructively removed from the wellbore casing.

According to the present invention, downhole tools including slips, drag blocks and buttons are disclosed which comprise light weight material treated by plasma electrolytic oxidation which provide the required anchoring downhole and which are easily removable following completion of an operation.

These and other advantages of the present invention will become apparent from the following description.

SUMMARY OF THE INVENTION

Downhole tools comprised of light material such as aluminum, dissolvable material, and light alloys treated by a plasma electrolytic process are disclosed. The tools are lighter than tools made of heat treated steel and have extremely high hardness, high strain tolerance, corrosion resistance and thermal and chemical stability. Moreover, the material is easily drill able. The plasma electrolytic oxidation process is a well known process. The tool is manufactured from the light material and then the portion requiring treatment is immersed in a liquid bath to undergo the plasma electrolytic oxidation process. The tools manufactured through the plasma electrolytic oxidation process in accordance with the present invention include but are not limited to slips, drag blocks and buttons. The buttons may also be used as pins.

Any downhole tool that has wear blocks to get drag or keep the tool centered may be manufactured in accordance with the present invention by utilizing the plasma electrolytic oxidation process.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention downhole tools are disclosed comprised of light material such as aluminum, dissolvable material, and light alloys. The light material is treated by the plasma electrolytic oxidation process. The tools are lighter than tools made of heat treated steel and have extremely high hardness which is higher than that of heat treated steel. Furthermore, those tools have high strain tolerance, corrosion resistance and thermal and chemical stability suitable for withstanding the high adverse pressure, temperature and pH conditions encountered downhole. Moreover, the material is easily drill able to open the sealed passages.

The plasma electrolytic oxidation process is a well known process which has been described in various publications. Plasma electrolytic oxidation is a bath-based method of producing ceramic layers on the surface of light alloys. The coatings are characterized by their wear resistance, corrosion resistance and thermal and chemical stability. The method is suitable for treating alloys of high aluminum, magnesium and titanium composition, but can also be applied to other metals such as zirconium, tantalum, niobium, hafnium and cobalt. The process is utilized by various manufactures such as Keronite Inc., 2121 Southtech Drive, Suite 220, Greenwood Ind. 46143, USA. More information about the process can be found at www.keronite.com. The process has been used to manufacture equipment components in many industries including automotive, aerospace, oil and gas.

In a typical manufacturing process of the tool, the tool is manufactured from the light material and then the portion requiring treatment is immersed in a liquid bath to undergo the plasma electrolytic oxidation process. Preferably, only the portion of the tool that needs to withstand the anchoring and centering forces is treated to strengthen it, with the remaining portion remaining untreated so that it can be easily be drilled or dissolved following the termination of the operation. The downhole tools manufactured through the plasma electrolytic oxidation process in accordance with the present invention include but are not limited to slips, drag blocks and buttons. The tools so formed have a Rockwell Hardness of greater than 55 C and very high wear resistance. Aluminum material, dissolvable material or other light weight alloy material may be used to make the tools by treating them with the plasma electrolytic oxidation process. Examples of dissolvable material include but are not limited to magnesium. Examples of light weight alloys include but are not limited to aluminum. Other material treatable by the plasma electrolytic oxidation process may also be used to make the tools by treating them with the plasma electrolytic oxidation process.

Slips manufactured in accordance with the present invention with the use of the plasma electrolytic oxidation process include wicker slips, hydraulic hold down slips and flat wedge slips. Because the slip products manufactured by that process have the above referenced qualities which would allow for the use of the slips downhole, the use of steel and carbide and ceramic inserts is eliminated. The tool is lighter and performs better that the previous tools that were made of steel and used carbide or ceramic inserts. Further the slips are easily drill able to open the sealed passages.

Similarly, in the case of drag blocks, the manufacturing of drag blocks from light material by using the plasma electrolytic oxidation process eliminates the use of heavy steel and carbide and ceramic inserts. The drag blocks so manufactured are lighter and perform better that the previous drag blocks that were made of steel and used carbide or ceramic inserts.

As regards buttons, the buttons manufactured from light material such as aluminum, light alloys or dissolvable material and having the coating formed by the plasma electrolytic oxidation as disclosed herein, are hard enough to bite the casing without the use of ceramic, carbide or steel when used in connection with slips or the like. These treated buttons, however, may be used in other applications in a downhole tool, including but not limited to, using the buttons as pins to hold a tool together before setting.

It should be understood that any downhole tool that would have a pad to keep the tool centered and contains carbide or other wear type buttons could be made without the buttons or the inserts by treating the block or pad with the plasma electrolytic oxidation process to eliminate the use of steel or inserts. This is due to the high wear resistance that the subject treatment imparts into the substrate metal or substance. Because of the wear resistance and ability of the part to bite into casing, all tools that have wear blocks to get drag or keep the tool centered may be manufactured in accordance with the present invention by utilizing the plasma electrolytic oxidation process.

While the invention is described with respect to specific embodiments, modifications thereof can be made by one skilled in the art without departing from the spirit of the invention. The details of said embodiments are not to be construed as limitations except to the extent indicated in the following claims. 

What is claimed is:
 1. An downhole tool, comprising: a body; and a coating formed by a plasma electrolytic process on the body.
 2. A downhole tool according to claim 1 wherein the tool is a slip.
 3. A downhole tool according to claim 2 wherein the slip is a wicker slip.
 4. A downhole tool according to claim 2 wherein the slip is a flat wedge slip.
 5. A downhole tool according to claim 2 wherein the slip is a hydraulic hold down slip.
 6. A downhole tool according to claim 1 wherein the tool is a drag block.
 7. A downhole tool according to claim 1 wherein the tool is a button.
 8. A downhole tool according to claim 1 wherein the body is constructed of aluminum.
 9. A downhole tool according to claim 1 wherein the body is constructed of dissolvable material.
 10. A downhole tool according to claim 1 wherein the body is constructed of a light alloy.
 11. A downhole tool according to claim 4 further including a button attached to the flat wedge slip.
 12. A downhole tool according to claim 1 wherein the coating is formed on a portion of the body.
 13. A process for making a downhole tool, comprising the steps: making a body; and treating the body by a plasma electrolytic process.
 14. A process according to claim 13 wherein the tool is a slip.
 15. An apparatus prepared by a process comprising the steps of: making a downhole tool body; and treating the downhole tool body by a plasma electrolytic process.
 16. An apparatus according to claim 15 wherein the downhole tool is a slip. 